The present invention is directed to a catalyst and a process for the selective production of para-dialkyl substituted benzenes, and particularly, an improved catalyst and a process for the selective production of para-dialkyl substituted benzenes using a silica-modified catalyst.
Processes for the selective production of para-dialkyl substituted benzenes are known in the art. For example, U.S. Pat. No. 4,090,981 to Rodewald discloses a method for making a catalyst particularly suitable for the selective production of para-dialkyl substituted benzenes wherein a porous crystalline aluminosilicate zeolite is coated with a silica and then subject to heating in an oxygen containing atmosphere at temperatures in excess of 300.degree. C. U.S. Pat. No. 4,117,026 to Haag et al. discloses the production of dialkylbenzenes by the disproportionation of monoalkylbenzenes over zeolites pretreated with difficultly reducible oxides, including magnesium oxide, or coke. U.S. Pat. No. 4,127,616 to Rodewald discloses a process wherein a monoalkyl-substituted benzene having 1-4 carbon atoms and a mixture of benzene with an alkylating agent containing 1-4 carbon atoms is mixed with a zeolite having a silica coating. U.S. Pat. No. 4,465,886 to Rodewald also discloses a silica-modified catalyst for use in the selective production of paradialkyl substituted benzenes. U.S. Pat. No. 4,477,583 to Rodewald relates to a method of preparing a composition having a crystalline zeolite with a coating of silica which is useful in the selective production of para-dialkyl substituted benzenes. These patents contemplate the use of zeolite catalysts synthesized in the presence of organonitrogen templates. Such catalysts, hereinafter referred to as "organic catalysts", are disclosed in U.S. Pat. No. 3,702,886 to Argauer et al.